Planetary ball mill



June 6, 1933. J. CRITES 1,912,762

PLANETARY BALL MILL l Filed Feb. ll, 1932 2 Sheets-Sheet l I Imrfen or June 6, 1933. J. CRITES PLANETARY BALL MILL Filed Feb. ll. 1932 2 Shee'ts-Sheet 2 and into a dischargechute. Preferably the the mill and again yPatented June 6, 1933 UNITED STATES J' OE CRITIES, OF EVANSTON, ILLINOIS, ASSIGNOR TO THE RAYMOND BROTHERS IIYIIEAL'I` PATENT OFFI/,CE

IPULVERIZER COMPANY, OF CHICAGO, ILLINOIS, A' CORPORATION OF ILLINOIS rLANE'rAnY BALL MILL Application led February 11, 1932. Serial No. 592,348.

This invention relates to certain new and useful improvements in planetary ball mills of the type in which an annular series of grinding balls is caused to revolve about a central vertical axis between relatively movable ball races -or grinding rings.

Briefly described, the improved grinding mill comprises a closed housing in the lower portion ofwhich are mounted the grinding elements consisting of one or more annular series of grinding balls adapted to revolve about a central vertical axis, and a plurality of relatively movable grindingyrings centered about this vertical axis and between which the balls are confined. A central vertical driven shaft serves to support and rotatei one or more of the grinding rings. Means is. provided for feeding material to be ground or pulverized into ,the upper portion of the housing and distributing thematerial so that it will fall by gravity between the grinding elements. The ground material falls by gravity to the bottom of the housing, and a rotary scraping means carried by the vertical shaft propels this material toward mill is used in combination with arnechanical separator of suitable type. The material discharged from the mill is conveyed to and into the separator, in which the fine material is separated out and collected The coarser material is returned from the separator into passes through the grinding process.

The mill disclosed andclaimed herein in.

provide an improved mill constructibn of the Y type briefly. described hereinabove and disclosed more in detail in the specifications ,which follow. t

v, Another object provide an improved mill of this type` embodyingr a, plurality of separate annular series of grindingballs becombination of elements for grinding or pul-v verizing material and separating outthe pulverized material. 1/

Other objects and advantages of this invention will be more apparent from the following detailed description of one approved form of apparatus built according to the principles of this invention.

In the accompanying drawings:

Fig. 1 is a central vertical section through the improved mill.

Fig. 2 is a horizontal section taken substantially on the line 2 2 of Fig. .1.

Fig. 3 is a horizontal section taken substantially on the line 3-3 of Fig. 1.

Fig. 4 is a diagrammatic elevation showing the improved mill in combination with a separator, together with means for circulating the material continuously through the two devices.

The improved mill comprises a closed housing indicated generally at 1, supported on any suitable form of base or pedestal 2.' The housing 1 may preferably be built up ofa plurality of superposcd sections comprisin the upper casing member 3 rovided Wit a normall ,closed opening 4 or permitting access to t e interior of the upper portion of the housing, a central annularsection 5 which surrounds and supports the grinding elements, a lower section 6 which provides the bottom 7 for the main grinding chamber 8, and 'a bottom casing member 9 which/.cooperates with member 6 to enclose a lower chamber `1.() containing elements of the driving gearing.

A vertical shaft l1 is rotatably supported centrally Within the housing, the upper end of this shafigbeing journaled in a bearing -12 carried by the upper housing member 3,

andthe lower end ofthe shaft being journaled in a suitable thrust bearing indicated generally at 13. A driving shaft 14 is jour-v loo naled in bearings 15 and 16 mounted in casing section 9 and carries a beveled pinion 17 which meshes with the beveled gear 18 keyed on the lower portion of vertical shaft 11. Any suitable means may be provided for lubricating the bearings and gearing.

In the present example, two similar annular series of grinding elements are providy ed, one superposed upon the other for successively acting on the material to be ground as it falls through the chamber 8. The upper grinding elements include an annular series of balls 19, and the lower grinding elements comprise a similar annular series of balls 20. An outer grinding ring 21, provided with an inner raceway 22 for the balls 29, is fixedly supported within housing section 5. Preferably the lower outer portion of ring' 21 is tapered downwardly and inwardly and fits against a correspondingly tapered surface within housing 5 as indicated at 23. A similar outer grinding ring 24 for the upper series of balls 19 is supported upon the lower ring 21, but is reversed so that its tapered outer surface eX- tends upwardly and inwardly as indicated at 25, and a wedge-shaped clamping ring 26 is adapted to be forced by screws 27 between this tapered surface 25 and the adjacent inner `wall of housing 5 so as t-o clamp the rings 21 and 24 firmly in place within the housing.

The balls 19 and 20 are engaged and supported from within by a plurality of inner rings 28, 29, 30 and 31. The grinding ring 29 is adapted to engage the inner lower portions of the upper balls 19, and the ring 30 is adapted to engage the inner upper portions of the balls 20, these inner rings 29 and 39 being secured by bolts 32 to a central frame or spider 33. A sleeve 34 is keyed on shaft 11 as indicated at 35, and is provided with outwardly projecting lugs 36. The frame 33 is shaped internally to fit loosely about the sleeve 34 and lugs 36 as indicated at 37 (Fig. 2). The lugs 36 will engage the frame 33 to cause the frame and the inner rings 29 and 30 to rotate with the shaft 11, but the assembly consisting of frame 33 and rings 29 and 30 1s permitted to adjust itself vertically, and is also permitted a limited amount of lateral movements due to the clearance between the frame and thesleeve 34 and lugs 36. The rings 29 and 30 are thus self-adjusting at all times into proper engagement with the balls 19 and 20. At the same time these inner rings are positively rotated from the vertical shaft 11. The upper in ner ring 28 engages the upper inner surfaces of balls 19, and is secured by bolts 38 to a spider 39 which loosely surrounds the shaft 11. In the same manner, the lower inner ring 31 which engages the lower inner faces of balls 20 is secured to a spider 40. A plurality (in5 the present example four) of socket members or cups 41 are mounted in the lower spider 40, and similar cups 42 are mounted in the upper spider 39. Vertically extending bolts 43 extend through the aligned cups 41 and 42 and through bolt openings provided in the central frame 33. The head 44 at the lower end of each bolt 43 seats in the lower cup 41, and a coiled compression spring 45 surrounding the upper portion of bolt 43 seats at its lower end in cup 42 and. bears at its upper end against a washer 46 held adjustably on bolt 43 by the nuts 47 threaded' on the upper end of the bolt. It will now be apparent that the bolts 43 bind the spiders 39 and40 and central frame 43 Atogether so that they will rotate in unison,

but the springs 45 constantly urge` the spiders 39 'and 40 toward one another and toward the central frame 33. .As a consequence, the inner grinding rings 28, 29, 30 and 3l will all rotate in unison, but the upper pair of rings 28 and 29 will be urged toward one another and into engagement with'the upper balls 19, while the lower rings 30 and 3l will be urged toward one another and into engagement with the lower series of balls 20. The entire inner assembly of grinding rings is freely adjustable vertically and laterally, and the inner rings are adjustable independently of one another, so that the assembly is self-adjusting to provide an equalized bearing engagement with the several balls at all times. It will be noted that the boltsl 43 are permitted a limited radial movement in the frame 33.

as also are the cups 42 and 41 in the upper and lower spiders 39 and 40, so that the several inner rings are permitted independent lateral movements to some extent. As will also be hereinafter apparent, the springs 45 will yield so that the inner rings can separate and permit the passagel of unusually large foreign bodies between the balls and the rings to avoid damage to the grinding mechanism.

Any suitable means may be provided for feeding the material to be ground into the upper portion of the housing and delivering it onto and between the upper grinding elements. In the example here shown, a horizontal table or disk. 48 mounted on vertical shaft49 within a casing 5() is rotated at a comparatively slow speed by means of reducing belt gearing 51 from the upper end of shaft 11. The material to be ground is fed onto table 48 through the delivery pipe or chute 52. A fixed blade or scraper causes the material deposited on rotating table 48 to be pushed ofi' into a chute 54 which extends down into the grinding chamber 8. A comparatively rapidly rotating distributing table or disk 55 has a hub 56 keyed at 57 -on the central shaft 11. Thematerial falls through hopper 54 onto the rotating table 55 and is thrown out centrifugally in all directions so as to fall between the upper series of balls 19 and the grinding rings 24, 28 and 29.

The number and size of the grin-ding balls is insufficient to form a complete circle, that is there will be a free space such as indicated at l58 in Fig. 2 remaining which may divide itself more or less equally between the balls or may become temporarily localized at some one or more points. This permits a certain 'amount of independent movement of the individual balls to' accommodate the material which isl ground between the balls and between the balls and the grin-ding rings; It is to be understood that the balls are entirely free except foi their rolling engagement with the grinding rings.

It will be understood that the lower series of balls 20 cooperates with the grinding rings 21, 3() and 31 in exactly the same manner, the partially ground material which falls from the upper grinding element being received by and passing down betweenthe lower series of grinding elements and being further ground. If desired, or found necessary, three or more series-of these grinding elements could be superposed one above the other by merely duplicating parts of the mechanism` already described.

The sleeve 34 (which is keyed to shaft 11 as already described) is formed with an outwardly flaring skirt portion 59 which rotates in close proximity to the bottom wall 7 of the housing. A plurality of Scrapers 60 are carried by this rotating skirt 59, 1n the example here shown the 'Scrapers being riveted at 61 to upwardly projecting'lugs 62 formed on the skirt member. A discharge chute 63 extends downwardly and outwardly from one outer edge portion of the lower housing member 6. The ground or partly ground material will fall from the .lower grindingelements into the lower portion of the housing and will be pushed around .by the scrapers 6() until it falls out through chute 63.

In operation, vthe drive shaft 14 will be rotated from any suitable source of power so as to rotate, through the beveled gearing 17 and 18, the vertical shaft 11. The rotation of this vertical shaft will cause the inner assembly of grinding rings 28, 29, 30 and 31 to rotate, and this will'cause the balls 19 and 20 to roll on-these inner rings and on-the outer rings 21 and 24 and thus to revolve with a planetary motion about the central vertical axis of shaft 11. The rotation of shaft 11 will cause the feedingand distributing tables 48 and 55 to rotate and to distribute the material to be ground onto the upper set of grinding elements between which it passes, being ground between the adjacent balls and between the balls and the grinding .rings on which the balls roll. The

material will then fall onto the lower set of' grinding elements where this operation is repeated. The ground and partially ground material finally falls into thd lower portion of the housing and is propelled by the rotating Scrapers 60 toward and into the discharge chute 63.

If hard or ungrindable material, vsuch as pieces of metal, should find their way into the mill, the Ainner grinding rings are adapted to spreadapart', againstthe resistance of springs 45, an-d thus permit the balls to move away 'from the rings suiiiciently to permit the passage of these ungrindable articles. The clearance 58 provided between the balls of each annular series also permits the passage of such material between the respective balls of the series.

It is preferred to use a mill of this type in a grinding and conveying circuit of the general type shown in Fig. 4. At 64 is shown a mechanical separator, preferably of the type disclosed and claimed in the patent to Walter M. Cook, No. 1,783,357, granted December 2, 1930. However, other suitable forms of separators might be used. The material to be ground is first delivered through a feed pipe 65 into and through the feed pipe 52 already described and thence into the mill. The partially ground or pulverized material is discharged from the mill through chute 63 into a suitable conveyor or elevator 66 which earries the material up and discharges it through chute 67 into the separator 64. The suiiiciently finely divided or pulverized material is discharged through central chute 68 and delivered through pipe 69 to any suitable collection receptacle. The coarser particles, which are not sufficiently pulverized, are delivered through chute 70 into the feed pipe 52 and thence passed again through the grlnding operation. It will thus be seen that the material will circulate continuously through this grinding and separating apparatus, only being discharged therefrom through pipe 69 when it has been pulverized to the desired degree.

I claim :l

1. In a planetary ball mill, a closed housing, a vertical shaft rotatably mounted therein, means for rotating the shaft, grinding elements comprising a series of balls adapted to travel in a horizontally disposed annular path, a plurality of grinding rings centered about the shaft between which the balls are confined; said rings including an outer ring fixed within the housing, and a pair of inner rings whichare-adapted to engage respectively the upper and lowerv inner portions of the. balls and force them outwardly into engagement with the fixed ring, the balls being free except for the rolling engagement with the rings, means for yieldably urging the inner rings toward one another and into engagement with the balls, connecting means Yfor rotating the inner rings `from the shaft within the upper portion of the housing for feeding material to be ground' above the grinding elements, and means for collecting and discharging from the housing` the material falling from the grinding elements.

2. In a planetary ball mill, a closed housing, a vertical shaft rotatably mounted therein, means for rotating the shaft, grinding elements comprising two separate series of balls adapted to travel in two superposed horizontally disposed annular paths, a plurality of grinding rings centered about the shaft between which the balls are confined, said rings including two outer grinding rings fixed within the housing, one for each series of balls, a pair of central inner rings iixed together and adapted to engage respectively the inner lower surfaces of the upper series of balls and the inner upper surfaces of the lower series of balls, an upper inner ring adapted to engage the inner upper surfaces of the upper series of balls, a lower inner ring adapted to engage the inner lower surfaces of the lower series of balls, mea-ns for yieldably urging the upper and lower inner rings toward the central inner rings, and connecting means for rotating the inner rings from the shaft, said connecting means including relatively movable parts whereby the inner rings are permitted limited lateral movements.

3. In a planetary ball mill, a closed' housing, a vertical shaft rotatably mounted therein, means for rotating the shaft, Agrind- .ing elements comprising two separate series of balls adapted to travel in two superposed horizontally disposed annular paths, a plurality of grinding rings centered about the shaft between which the balls are confined,

said rings including two outer rinding rings fixed within the housing, one or ,each series of balls, a pair of central inner rings fixed together and adapted to engage respectively the inner lower surfaces of the upper series -of balls and the inner upper surfaces of the lower series of balls, an upper inner ring adapted to engage the inner upper surfaces of the upper series of balls, a lower inner ring adapted to engage the inner lower surfaces of the lower series of balls, means for yieldably urging the upper and lower inner rings toward the central inner rings, and means connecting the central inner rings with the shaft for rotating the rings, saidv connecting means including relatively movable parts whereby the inner rings are permitted limited lateral movements. D

4. In a planetaryball mill, a closed housing, a vertical shaft rotatably mounted therein, means for rotating the shaft, grinding elements comprising two separate Series of balls adapted to travel in twosuperposedhorizontally disposed annular paths, a plurality of grinding rings centered about the shaft between which the balls are confined, said rings including two outer grinding rings lixed within the housing, one for each series of balls, a pair of'centralinner rings fixed together and adapted to engage respectively. the inner lower surfaces of the upper series of balls and the inner upper surfaces of the lower series of balls, an upper inner ring adapted to engage the inner upper surfaces of the upper series of balls, a lower inner ring adapted to engage the inner lower surfaces of the lower series of balls, means for yieldably urging the upper and lower inner rings toward the central inner rings, and connecting means for rotating the inner rings from the shaft, said connecting means including relatively movable parts' whereby the inner rings are permitted limited lateral movements, means in the upper portion of the housing for distributing' material to be ground above the upper series of balls, an outlet chute extending from one outer edge of the'bottom of the housing, and a rotary scraper carried by the shaft for propelling the material falling from the grinding elements toward and into the chute.

5. In a planetary ball mill, a closed housing, a vertical shaft rotatably mounted therein, means for rotating the shaft,vgrinding elements comprising two separate series of balls adapted to travel in two superposed horizontally disposed annular paths,v a plurality of grinding rings centered about the shaft between which the balls are confined, said rings including two outer grinding rings fixed within the housing, one for each series of balls, a pair of central inner rings fixed together and adapted to engage respectively the inner lower surfaces of the upper series of balls and the inner upper surfaces of the lower series of balls, an upper inner ring adapted to engage the inner upper surfaces of the upper series of balls, a lower inner ring adapted to engage the inner lower surfaces of the lower series of balls, means for connecting the upper and lower rings tothe cen- Ytral rings for rotation therewith and for yieldingly urging the upper and lower rings toward the central rings, said means permitting limited lateral relative movements of the rings, and means for connecting the central rings with the shaft so that the inner ring assembly will rotate with the shaft, said latter connecting means including relatively movable parts whereby the inner ring assemblyis permitted vertical movement and limited lateral movement with relation to the shaft.

6. In a planetary ball mill, a closed housing, a vertical shaft rotatably mounted therein, means for rotating the shaft, grinding ele'- ments comprising two separate series of balls adapted to travel in two superposed horizontally disposed annular paths, a plurality of grinding rings centered about the shaft between which the balls are confined, said rings including two outer grinding rings fixed within the housing, one for each series of balls, and an assembly of inner rings comprising two palrs of rings, the

rings of one pair engaging respectively the upper and lower inner portions of the upper series of balls, and the rings of the other pair similarly engaging the balls of the lower series, means for yieldably urging the rings of each pair toward one another, and means connecting the inner ring assembly with the shaft for rotating the inner rings, said connecting means including relatively movable parts whereby the inner rings are permitted limited lateral movements. A

' JOE CRITES. 

